The present invention relates to a control method for engine valve actuation.
In U.S. Pat. No. 6,009,841, an engine with a hybrid valvetrain is disclosed in which one intake valve is actuated by a source other than a camshaft. This first intake valve is randomly operable meaning that the valve opening and closing events are independent of engine crankshaft position, thus, a fully variable valve. A second intake valve is actuated by a camshaft and includes a deactivator. Operation of the second valve may be discontinued or restored within one engine cycle, termed selectable intake valve herein. The exhaust valve(s) of the hybrid valvetrain is conventionally camshaft actuated. As disclosed in U.S. Pat. No. 6,009,841, the advantage of such a system over fully camless engine operation is improved fuel economy.
In U.S. Pat. No. 6,009,841, the method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lowest range in torque, using a selectable intake valve when the engine is operating in a medium range in torque, and using both the randomly operable intake valve and the selectable intake valve when the engine is operating in a highest range in torque.
In U.S. Pat. No. 5,647,312, a method is described in which air is admitted using a randomly operable intake valve when the engine is operating in a lower range in torque and speed and air is admitted using a selectable intake valve when the engine is operating at higher speed or higher torque.
Both U.S. Pat. No. 6,009,841 and U.S. Pat. No. 5,647,312 teach that making transitions among operating modes involves activating and deactivating valves. The inventors herein have recognized that by simply turning valves on and off leads to large excursions in engine torque which would be noticeable and annoying to the operator. The inventors herein have also recognized that the potential for hybrid valvetrain fuel economy benefits, as disclosed in U.S. Pat. No. 6,009,841, depends on suitable methods to accomplish transitions between operating modes; otherwise, the fuel efficiency potential is unrealized.
A method for controlling an internal combustion engine, the engine containing at least one cylinder, a randomly operable intake valve, a selectable intake valve with a predetermined closing time, a throttle valve in the engine""s intake system, and an engine control unit, is provided. The method includes the steps of providing a randomly operable intake valve closing time which is after the predetermined valve closing and initiating operation of the selectable intake valve. In a further step, the throttle valve is closed and the randomly operable intake valve closing time is advanced so that substantially constant engine torque is provided.
A method for controlling an internal combustion engine, the engine containing at least one cylinder, a randomly operable intake valve, a selectable intake valve with a predetermined valve closing time, a throttle valve in the engine""s intake system, and an engine control unit, has a first step of activating the randomly operable intake valve with a closing time after the predetermined valve closing time and a second step of opening the throttle valve and retarding the randomly operable intake valve closing time.
A method for controlling an internal combustion engine, the engine containing at least one cylinder, a randomly operable intake valve, a selectable intake valve with a predetermined valve closing time, a throttle valve in the engine""s intake system, and an engine control unit, has a first step of advancing a randomly operable intake valve closing time and closing the throttle valve and a second step of ceasing operation of the randomly operable intake valve when additional advancement of the randomly operable intake valve closing time has no appreciable effect on inducted air remaining in the cylinder after closing of the randomly operable intake valve.
A method for controlling an internal combustion engine, the engine containing at least one cylinder, a randomly operable intake valve, a throttle valve in the engine""s intake system, and an engine control unit, has the steps of closing the throttle valve and advancing a randomly operable intake valve closing time, in the event that the randomly operable intake valve closing time is retarded from a predetermined valve closing time and closing the throttle valve and retarding a randomly operable intake valve closing time, in the event that the randomly operable intake valve closing time is advanced from the predetermined valve closing time. The predetermined valve closing time is that which maximizes air inducted which is retained in the cylinder after closing of the randomly operable intake valve.
A method for controlling an internal combustion engine, the engine containing at least one cylinder, a randomly operable intake valve, a throttle valve in the engine""s intake system, and an engine control unit, has the steps of opening the throttle valve and advancing a randomly operable intake valve closing time, in the event that the randomly operable intake valve closing time is advanced from a predetermined valve closing time and opening the throttle valve and retarding a randomly operable intake valve closing time, in the event that the randomly operable intake valve closing time is retarded from the predetermined valve closing time.
The advantages of the above methods are numerous. The transitions among operating modes provide a smooth torque trajectory. Thus, the transitions are not detectable by the operator. The time over which a transition occurs is brief, two to twenty engine cycles. The methods disclosed herein permit realization of the fuel efficiency potential of an engine with a hybrid electric valvetrain.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.